Delay-action motor energizing control devices

ABSTRACT

THIS CONTROL DEVICE, FOR THE DELAY-ACTION ENERGIZATION OF AN ELECTRIC MOTOR OF THE TYPE ADAPTED TO BE BRAKED BY SHORT-CIRCUITING THE ARMATURE DRIVING A MECHANISM HAVING A PREDETERMINED FIXED-STOP POSITION, COMPRISES A FIXED-STOP DEVICE FOR SHORT-CIRCUITING SAID ARMATURE AND A THERMAL DELAY-ACTION DEVICE ASSOCIATED WITH SAID FIXED-STOP DEVICE FOR RESTARTING THE MOTOR AFTER A PREDETERMINED TIME PERIOD. IT UTILIZES A HEATING-WIRE THERMAL DELAY-ACTION DEVICE WHEREIN THE HEATING WIRE PROPER IS OPERATIVELY CONNECTED TO A CONTACT ARM MOVABLE BETWEEN A MOTOR ENERGIZING CONTACT AND AN ARMATURE SHORT-CIRCUITING CONTACT AGAINST WHICH SAID WIRE IS NORMALLY URGED IN ITS COLD CONDITION.

United States Patent DELAY-ACTION MOTOR ENERGIZING CONTROL DEVICES 6 Claims, 2 Drawing Figs.

U.S.Cl 318/471,

1 318/472 Int. Cl H02h 7/08 Field of Search 318/466, 471, 472

[56] References Cited UNITED STATES PATENTS 3,253,206 5/1966 Romanowski 3 l 8/472X 3,497,790 2/1970 Tixier 3l8/466 Primary Examiner-Benjamin Dobeck Attorney-Stevens, Davis, Miller and Mosher ABSTRACT: This control device, for the delay-action energization of an electric motor of the type adapted to be braked by short-circuiting the armature driving a mechanism having a predetermined fixed-stop position, comprises a fixed-stop device for short-circuiting said armature and a thermal delayaction device associated with said fixed-stop device for restarting the motor after a predetermined time period. it utilizes a heating-wire thermal delay-action device wherein the heating wire proper is operatively connected to a contact arm movable between a motor energizing contact and an armature short-circuiting contact against which said wire is normally urged in its cold condition.

DELAY-ACTION MOTOR ENERGIZING CONTROL DEVICES The present invention relates to a control device for the delay-action energization of an electric motor of the type adapted to be braked by short-circuiting its armature by means of a so-called fixed-stop" device designed for stopping the mechanism in a predetermined position. a current application of a device of this character being found in windscreen wipers of automobile vehicles.

Control devices of this type are already known wherein the delayed or intermittent energization of the motor, which involves the operation of the mechanism at predetermined time intervals, is obtained by using thermal time-lag means coacting with the fixed stop device for obtaining the desired inoperative time periods of the mechanism.

Hitherto known devices are of the single or double metallic strip type and are characterized by a rather detrimental thermal inertia during the cooling phase; besides, they are sensitive to the surrounding temperature and tend to diverge from the predetermined rate of operation after a prolonged service, thus introducing undesired irregularities in the desired operation and making it difficult to produce a short effective operating cycle of the mechanism at the desired time intervals.

it is the object of the present invention to provide a control device of the type broadly set forth hereinabove which is free of the inconveniences characterizing hitherto known devices in that it utilizes a thermal delayaction device of the heating wire and differed-heating type, but of which the low thermal inertia is advantageously utilized during the cooling phase for obtaining the desired operation in a reliable and yet simple manner.

More particularly, the device according to this invention is characterized essentially in that said thermal delay-action device comprises a heating wire of the differed-heating type which is operatively connected to a contact arm moyable between a motor energizing contact and an armature shortcircuiting contact, said contact arm being normally urged by the heating wire, in its cold position, against said lastnamcd armature short-circuiting contact, and constantly electrically connected to one of the fixed contacts of a reversing switch incorporated in a fixed stop device causing said one fixed contact to be closed in said predetermined stop position, the other fixed contact of said reversing switch constituting a temporary motor energizing contact.

In order to afford a clearer understanding of this invention, two typical forms of embodiment of the device constituting the subject-matter thereof will now be described by way of example with reference to the attached drawing, in which:

FlG. l is wiring diagram of the device, shown in its inoperative position, and

FIG. 2 is a wiring diagram concerning a modified form of embodiment of the device.

Referring to FIGS. 1 and 2, it will be seen that the electric motor M (for example the driving motor of a windscreen wiper of an automobile vehicle) has its armature operatively connected to a fixed-stop device comprising a cam l driven by said armature and adapted to actuate the movable contact arm of a reversing switch 2 having a motor energizing contact 2a and an armature short-circuiting contact 20.

A manual ON-OFF switch 3 is provided for controlling the normal continuous operation of the windscreen motor and a switch 4 is also provided for the time-lag, delayed-action or intermittent operation, wherein a thermal delay-action device is adapted to operate by coacting with said reversing switch 2 of the fixed stop device. The assembly is supplied with electric current from a storage battery (not shown), having a positive polarity and a negative polarity T.

The thermal delay-action device consists of a heating wire 6 connected to a contact arm 7 adapted, according as the wire 6 is expanded or contracted, to engage either a first contact 50 connected to the negative polarity T, or another contact b connected to the positive polarity in conjunction with the force of a tension spring 8 and the action of a solenoid 9 in the case illustrated in FIG. 1, and with the action of a tension spring 8 and ofa bistable spring 10 ofthe rolling or other type, in the case illustrated in FIG. 2, this last-named spring assisting in ensuring the stability of the contact arm in either position thereof. I

The heating wire 6, in its normal, contracted state obtaining when no current flows therethrough, urges the arm 7 for engagemcnt with the Contact 5a. It can be energized via switch 4 consisting preferably of a rheostat switch, as illustrated, and associated with a resistor ll, so that the delay-action characteristic ofthe device can be adjusted as required.

The cam l of the fixed stop device is adapted to cause the reversing switch contact arm 2 to engage contact 20 during the fraction ofa revolution necessary for stopping the motor when its armature is shortcircuited, this fraction being increased for warranting the safe holding of the contact 20 in its closed con dition after the motor has been stopped.

The motor, its fixed-stop device, the delay-action device, the ON-OFF switch 3 and rheostat switch 4 are on the other hand so interconnected that the control system operates as follows:

.In the case illustrated in FIGS. 1 and 2, when the movable arm of ON-OFF switch 3 engages contact m (ON), the armature is constantly energized and therefore the motor drives the windscreen wiper continuously; on the other hand, when the contact arm of switch 3 engages its other contact a (OFF), the armature remains energized if the contact arm of switch 2 cm gages contact 2a (connected to the positive terminal and thusthe motor keeps rotating until the cam of the fixed stop device causes the switch arm to engage the other contact 2c. Under these conditions, the armature is short-circuited, contact 2c being normally connected to the negative polarity by the contact arm 7 and contact 5a of the delay-action device, as already explained hereinabove. Thus, the windscreen wiper will always stop in a predetermined position.

With the contact arm of switch 3 engaging its OFF contact a, the delayed-action operation of the windscreen wiper is obtained by closing the circuit including the rheostat switch 4.

in the case illustrated in FIG. 1, the heating wire 6 is heated by the current flowing through it and also through the contact arm 7, and contact 50 branched off the motor armature M to which the contact arm 7 is also connected via contact 2c of reversing switch and contact a of the ON-OFF switch 3. Due to the expansion of wire 6, the tractive force of spring 8 causes the contact arm 7 to move away from contact 511 and urges said arm against the other contact 5b; however, it will be noted that after the opening ofcontact 5a and before the closing of contact 5b the current keeps flowing through the heating wire 6 and the motor armature, but this current is too weak to cause the motor operation, as the armature resistance is lower than that of the assembly 4, 11 and 6. Immediately as contact 5b is closed, the armature is energized directly from this contact via the contact arm and contacts 20 and a, whereby the windscreen wiper motor is started. The starting of motor M causes the cam 1 of the fixed stop device to open contactZc and then close contact 2a, so that the motor is kept in its energized condition by this last contact and the solenoid 9 of which the energization will cause the contact arm 7 to be attracted for engagement of contact 50 and thus resume its initial position preliminary to the short-circuiting of the motor armature. This short-circuiting will take place immediately as the cam 1 causes the contact arm of reversing switch 2 to move from contact 20 to contact 2c, the time-lag or delay-action device being restored likewise to its initial condition while solenoid 9 is deenergized.

This operation may be based for example on an order of magnitude of the cycle periods which is of one second per revolution for the fixed-stop cam l, the contact 2c being closed during one-tenth of a revolution, of a multiple of this time, such as 4 to 8 seconds for the time-lag introduced by the wire heating necessary for moving the movable arm 7 from contact 5a to contact 5b (the resistor 11 and the switch rheostat being calculated accordingly), and it may be pointed out that the wire cooling may be considered as effective during the time of the fraction of a second which corresponds to the return of contact arm 7 from contact 5b to contact 5a; in other words, the time period for reheating the wire which then elapses before the armature is again short-circuited remains inferior to one second and therefore constitutes but one fraction of the aforesaid time-lag, before a new cycle commences. Alternately, it is a simple matter to keep the wire 6 in its cooled state until the armature is short-circuited, by causing in this case the connection between contact 5a and the negative polarity T to include an additional contact arm of the reversing switch of the fixed-stop device, so that this additional contact arm will close this circuit section 511 to the negative polarity only simultaneously with contact 2c.

In the case illustrated in H0. 2, it will be noted that the heating wire 6 is electrically insulated from contact arm 7 and connected to the terminal of the contact arm of reversing switch 2 via a conductor 12. When the rheostat switch 4 is connected to the circuit, the wire 6 is heated by the current flowing through it and also through the circuit elements 4, ll, 6, l2 and then 2c, 7 and 5a, which constitutes a privileged branch with respect to the connection leading to the negative polarity T and passing through the motor armature M. When the heated wire 6 is expanded, the tractive force of spring 8 moves the contact arm 7 away from contact 5a, but after contact 5a is open and before contact 5!; is closed the current flows through the heating wire 6 and also through the motor armature M, but this current is still too weak to cause the rota tion of the motor. Beyond a certain intermediate position between contacts 5a and 5b, the rolling spring 10 adds its force to that of spring 8 for pressing the contact arm 7 against contact 5b.

When this contact 5b is closed, the armature is energized directly from 5b through elements 7, 2c and 11, thus starting the windscreen wiper motor.

Once the motor is started, the rotation of cam 1 opens contact 2c and closes contact 2a, whereby the motor is kept in its energized condition through this last-named contact.

It will be noted that in this example it is preferred to retard the cooling of wire 6 in order safely and positively to keep the contact arm 7 in engagement with contact 5b until the starting of motor M has caused cam l to open contact 20, this opening being relayed, as far as the motor energization is concerned, by the closing of contact 2a.

This condition is obtained by using a resistor 13 branched off the negative polarity between the aforesaid resistance 11 and the heating wire 6. Thus, when the contact arm 7 engages contact 5b, a current for keeping the wire 6 in its heated condition flows via circuit elements 5b, 7, 2c, 12, 6 and 13. Of course, the ohmic value of resistor 13 is higher than that of the combined resistance of elements 11 and 4, and also ofthe wire 6. However, during the switching back of reversing switch 2 from contact 2c to contact 2a, no current flows through wire 6 and since it cools down immediately it causes the contact arm 7 to be attracted again to contact 5a and pressed thereagainst by the spring it) beyond a certain intermediate position of said contact arm between contacts 5a and 5!).

It will also be noted that as a consequence of the closing of contact 211 the aforesaid holding or sustaining current circulation is resumed through the heating wire 6 and resistor 13, but its value is such that it cannot prevent the contact arm 7 from reengaging the contact 50, even if this return movement took place when contact was closed, and furthermore this current produces a wire heating effect considerably lesser than that required for operating the delay-action device through the heating circuit proper including the rheostat switch 4.

When the rotation of cam 1 causes the contact arm of the reversing switch to move from contact 20 to contact 2c, the motor armature M is short-circuited via circuit element 0 (OFF), 2c, 7 and 5a, and the motor is stopped immediately while the device resumes its initial condition, ready for another cycle, due to the closing of contact 20 of the heating wire 6 ofthe thermal delay-action device, whereby an adl'ustable idle period is introduced between the successive cyc es of operation of the motor, as long as the rheostat switch 4 is kept in the circuit.

it will be noted that the bistable spring 10 and resistor 13 are also applicable to the form of embodiment illustrated in FIG. I, for the same purposes as those set forth hereinabove.

Of course, other modifications concerning the combination of a heating-wire thermal delay-action device with a fixed stop device for a motor may occur to those skilled in the art without departing from the spirit and scope of the invention.

We claim:

1. An electrical control circuit for the delay-action energization of an electric motor of the type adapted to be braked by short-circuiting the armature and driving a mechanism hav-- ing a predetermined fixed-stop position, which circuit comprises a fixed-stop device for short-circuiting said armature, a thermal delay-action device for restarting the motor after a predetermined time period, and manual control members for energizing said motor and said delay-action device, said thermal delay-action device comprising a heating wire connected to a contact arm movable between a motor energizing contact and a motor armature short-circuiting contact against which said contact arm is normally urged by the wire in its cold condition, said fixed-stop device comprising a reversing switch, said movable contact arm being electrically connected to one of the fixed contacts of said reversing switch, said reversing switch adapted to close with said one contact in said predetermined fixed-stop position, the other contact of said reversing switch being a temporary motor-energizing contact.

2. A control circuit according to claim 1, wherein said manual control members comprise a motor ON-OFF switch interposed between said fixed-stop reversing switch and said armature, and a rheostat switch connected to said heating wire by means ofa resistor for energizing said delay-action device.

3. A control circuit according to claim 1, further comprising a first spring acting on said movable contact arm in opposition to said wire, and a solenoid acting on said movable contact arm in opposition to said spring, said solenoid being energized by said temporary motor-energizing contact.

4. A control circuit according to claim 1, further comprising a first spring acting on said movable contact arm in opposition to said heating wire and a second spring ensuring a bistable operation of said movable contact arm.

5. A control circuit according to claim 4, wherein said heating wire is electrically insulated from said movable contact arm and is electrically connected to a movable contact arm of said reversing switch.

6. A control circuit according to claim 5, wherein said wire is heated by a circuit which comprises said contact arm, a corresponding motor energizing contact, and said reversing switch, and further comprising a resistor branched off said heating circuit for retarding the cooling of said wire. 

